Respiratory motion correction in oncologic PET using T1-weighted MR imaging on a simultaneous whole-body PET/MR
Christian Würslin1, Holger Schmidt, Petros Martirosian
1Diagnostic and Interventional Radiology, Department of Radiology, University of Tübingen, Tübingen, Germany.
Unlabelled:
Hybrid PET/MR combines the exceptional molecular sensitivity of PET with the high resolution and versatility of MR imaging. Simultaneous data acquisition additionally promises the use of MR to enhance the quality of PET images, for example, by respiratory motion correction. This advantage is especially relevant in thoracic and abdominal areas to improve the visibility of small lesions with low radiotracer uptake and to enhance uptake quantification. In this work, the applicability and performance of an MR-based method of respiratory motion correction for PET tumor imaging was evaluated in phantom and patient studies.
Methods:
PET list-mode data from a motion phantom with (22)Na point sources and 5 patients with tumor manifestations in the thorax and upper abdomen were acquired on a simultaneous hybrid PET/MR system. During the first 3 min of a 5-min PET scan, the respiration-induced tissue deformation in the PET field of view was recorded using a sagittal 2-dimensional multislice gradient echo MR sequence. MR navigator data to measure the location of the diaphragm were acquired throughout the PET scan. Respiration-gated PET data were coregistered using the MR-derived motion fields to obtain a single motion-corrected PET dataset. The effect of motion correction on tumor visibility, delineation, and radiotracer uptake quantification was analyzed with respect to uncorrected and gated images.
Results:
Image quality in terms of lesion delineation and uptake quantification was significantly improved compared with uncorrected images for both phantom and patient data. In patients, in head-feet line profiles of 14 manifestations, the slope became steeper by 66.7% (P = 0.001) and full width at half maximum was reduced by 20.6% (P = 0.001). The mean increase in maximum standardized uptake value, lesion-to-background ratio (contrast), and signal-to-noise ratio was 28.1% (P = 0.001), 24.7% (P = 0.001), and 27.3% (P = 0.003), respectively. Lesion volume was reduced by an average of 26.5% (P = 0.002). As opposed to the gated images, no increase in background noise was observed. However, motion correction performed worse than gating in terms of contrast (-11.3%, P = 0.002), maximum standardized uptake value (-10.7%, P = 0.003), and slope steepness (-19.3%, P = 0.001).
Conclusion:
The proposed method for MR-based respiratory motion correction of PET data proved feasible and effective. The short examination time and convenience (no additional equipment required) of the method allow for easy integration into clinical routine imaging. Performance compared with gating procedures can be further improved using list-mode-based motion correction.
Insights
This study demonstrates an effective MR-based method for correcting respiratory motion in PET/MR imaging, significantly improving tumor visibility and quantification. The technique is feasible for clinical integration, offering enhanced PET tumor imaging without extra equipment.
Area of Science:
- Medical Imaging
- Radiochemistry
- Biophysics
Background:
- Hybrid PET/MR combines PET's sensitivity with MR's resolution.
- Respiratory motion degrades PET image quality, especially in thoracic/abdominal regions.
- MR-based motion correction can enhance PET image quality and quantification.
Purpose of the Study:
- To evaluate the applicability and performance of an MR-based respiratory motion correction method for PET tumor imaging.
- To assess improvements in lesion visibility, delineation, and radiotracer uptake quantification.
Main Methods:
- Acquired simultaneous PET/MR data from a motion phantom and 5 patients.
- Used MR navigator data to track diaphragm motion throughout PET scans.
- Applied MR-derived motion fields to coregister PET data, creating motion-corrected datasets.
Main Results:
- MR-based motion correction significantly improved lesion delineation and uptake quantification compared to uncorrected PET images.
- Key metrics like SUVmax, contrast, and SNR increased, while lesion volume decreased.
- Performance was comparable to gating, with no observed increase in background noise.
Conclusions:
- MR-based respiratory motion correction is feasible and effective for PET tumor imaging.
- The method is easily integrated into clinical routine due to short scan times and no need for additional equipment.
- Further improvements are possible with list-mode-based motion correction techniques.
